Hydrocarbon conversion catalyst for use in selectively making middle distillates

ABSTRACT

A hydrocarbon conversion catalyst useful for converting hydrocarbon feeds to midbarrel products is prepared by extruding a mixture of an inorganic refractory oxide component and a crystalline aluminosilicate zeolite having cracking activity to form extrudates which are broken into particles normally ranging in length between 1/16 and 1/2 inch. The extruded particles are then calcined in the presence of steam at a water vapor partial pressure greater than about 2.0 p.s.i.a., preferably greater than about 5.0 p.s.i.a. The calcination step is carried out in the presence of sufficient steam for a sufficient amount of time at a sufficient temperature to convert the crystalline aluminosilicate zeolite in the extrudates into an ultrahydrophobic zeolite having a unit cell size between about 24.20 and about 24.45 Angstroms and a sorptive capacity for water vapor less than about 5 weight percent of the zeolite at 25° C. and a p/p° value of 0.10.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a division of U.S. Ser. No. 830,139, filed in theUnited States Patent and Trademark Office on Jan. 31, 1992 and now U.S.Pat. No. 5,288,396, which is a division of U.S. Ser. No. 573,735, filedin the United States Patent and Trademark Office on Aug. 28, 1990 andnow U.S. Patent No. 5,116,792, which is a continuation of U.S. Ser. No.332,517, filed in the United States Patent and Trademark Office on Mar.31, 1989 and now U.S. Patent No. 4,990,476 which is acontinuation-in-part of U.S. Ser. No. 196,942, filed in the UnitedStates Patent and Trademark Office on Apr. 4,1988and now U.S. Pat. No.4,879,019, which is a division of U.S. Ser. No. 28,654, filed in theUnited States Patent and Trademark Office on Mar. 20, 1987 and now U.S.Pat. No. 4,762,813, which is a continuation of U.S. patent applicationSer. No. 793,567, filed in the United States Patent and Trademark Officeon Oct. 31, 1985 and now abandoned, which is a continuation-in-part ofU.S. patent application Ser. No. 699,919, filed in the United StatesPatent and Trademark Office on Feb. 8, 1985 and now U.S. Pat. No.4,610,973, which is a continuation of U.S. patent application Ser. No.531,924, filed in the United States Patent and Trademark Office on Sep.13, 1983 and now U.S. Pat. No. 4,517,074, which is a division of U.S.patent application Ser. No. 84,761, filed in the United States Patentand Trademark Office on Oct. 15, 1979 and now U.S. Pat. No. 4,419,271.The disclosure of U.S. Pat. No. 4,762,813 is hereby incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

This invention relates to a hydrocracking process and a catalyst for usetherein. The invention is particularly concerned with a catalystcontaining an ultrahydrophobic zeolite which, when used as ahydrocracking catalyst, selectively yields middle distillates.

Petroleum refiners often produce desirable products such as turbinefuel, diesel fuel, and other products known as middle distillates, aswell as lower boiling liquids, such as naphtha and gasoline, byhydrocracking a hydrocarbon feedstock derived from crude oil. Feedstocksmost often subjected to hydrocracking are gas oils and heavy gas oilsrecovered from crude oil by distillation. A typical gas oil comprises asubstantial proportion of hydrocarbon components boiling above about700° F., usually at least about 50 percent by weight boiling above about700° F. A typical heavy gas oil normally has a boiling point rangebetween about 600° F. and 1050° F.

Hydrocracking is generally accomplished by contacting, in an appropriatereaction vessel, the gas oil or other feedstock to be treated with asuitable hydrocracking catalyst under conditions of elevated temperatureand pressure in the presence of hydrogen so as to yield a productcontaining a distribution of hydrocarbon products desired by therefiner. Although the operating conditions within a hydrocrackingreactor have some influence on the yield of the products, thehydrocracking catalyst is the prime factor in determining such yields.At the present time middle distillates are not in high demand relativeto gasoline in the United States, however, marketing surveys indicatethat there will be an increased demand for middle distillates as theyear 2000 approaches. For this reason refiners have recently beenfocusing on midbarrel hydrocracking catalysts which selectively producemiddle distillate fractions, such as turbine fuel and diesel fuel, thatboil in the 300° F. to 700° F. range.

The three main catalytic properties by which the performance of amidbarrel hydrocracking catalyst is evaluated are activity, selectivity,and stability. Activity may be determined by comparing the temperatureat which various catalysts must be utilized under otherwise constanthydrocracking conditions with the same feedstock so as to produce agiven percentage, normally about 60 percent, of products boiling below700° F. The lower the activity temperature for a given catalyst, themore active such a catalyst is in relation to a catalyst of higheractivity temperature. Selectivity of hydrocracking catalysts may bedetermined during the foregoing described activity test and is measuredas the percentage fraction of the 700° F.--product boiling in themidbarrel product range of 300° F. to 700° F. Stability is a measure ofhow well a catalyst maintains its activity over an extended time periodwhen treating a given hydrocarbon feedstock under the conditions of theactivity test. Stability is generally measured in terms of the change intemperature required per day to maintain a 60 percent or other givenconversion.

As pointed out in U.S. Pat. No. 4,401,556, the disclosure of which ishereby incorporated by reference in its entirety, hydrocrackingcatalysts containing crystalline aluminosilicate zeolites generally havehigh activity but relatively poor selectivity for middle distillateproducts. Because of this, midbarrel hydrocracking catalysts normallyemploy an amorphous inorganic oxide base containing no zeoliticcomponent. Such catalysts, although selective for middle distillates,are not nearly as active as a catalyst containing a zeolitic component.U.S. Pat. No. 4,401,556 discloses a midbarrel hydrocracking catalystcontaining an ultrahydrophobic crystalline aluminosilicate zeolite whichcatalyst possesses both high activity and high selectivity for producingmiddle distillates. According to the patent, the selectivity of theultrahydrophobic zeolite component is abnormally high while the activityand stability of the zeolite are not impaired when compared to otherknown zeolite supports. The ultrahydrophobic zeolite is prepared from aY type zeolite starting material having a silica-to-alumina mole ratioof from about 4.5 to about 6.0 and a sorptive capacity for water vaporof at least 6 weight percent at 25° C. and a p/p° value of 0.10 bycalcining the zeolite powder in an environment comprising from 0.2 toabout 10 atmospheres absolute of steam at a temperature ranging from725° C. to 870° C. for a period of time sufficient to reduce thezeolite's sorptive capacity for water vapor to less than 5 weightpercent at 25° C. and a p/p° value of 0.10.

Midbarrel hydrocracking catalysts have been prepared using one of theultrahydrophobic zeolites disclosed in U.S. Pat. No. 4,401,556 bysubjecting the zeolite to an ammonium exchange and then mixing theammonium-exchanged ultrahydrophobic zeolite with an inorganic refractoryoxide component and an alumina binder material. The resultant mixture isthen extruded through a die to form extrudates which are dried at 120°C. and subsequently calcined in air at 900° C. The calcined extrudatesare then impregnated with a solution of nickel and tungsten components,dried and again calcined in air. It has now been surprisingly found thatdifferent batches of hydrocracking catalysts prepared in accordance withthe above-disclosed procedure have varying selectivities for middledistillates, some of which selectivities are relatively low. Thecommercial use of a midbarrel hydrocracking catalyst with lower thandesired selectivity for middle distillates will result in a loss of thedesired middle distillate product.

Accordingly, it is one of the objects of the present invention toprovide a midbarrel hydrocracking catalyst containing anultrahydrophobic zeolite, and a method for preparing such a catalyst,which is useful in hydrocracking and has high selectivity for middledistillates, which selectivity does not substantially vary from onebatch of catalyst to another. This and other objects of the inventionwill become more apparent in view of the following description of theinvention.

SUMMARY OF THE INVENTION

It has now been found that catalysts containing ultrahydrophobiczeolites prepared by calcining a Y zeolite powder in steam have varyingselectivities for middle distillate products. It is believed that thisvariability in selectivity is caused by the difficulty in commercialoperations of uniformly steam calcining the small particles whichcomprise the zeolite powder. It has been further found that the observedvariance in selectivities can be substantially avoided by postponing thesteam calcination step until after the Y zeolite powder has beenincorporated into the catalyst extrudates. Accordingly, the invention isdirected to a catalyst composition prepared by a process in which amixture of one or more inorganic refractory oxide components and acrystalline aluminosilicate zeolite having cracking activity is extrudedto form extrudate particles which are subsequently calcined in thepresence of steam at a water vapor partial pressure greater than about2.0 p.s.i.a., preferably greater than about 5 p.s.i.a. In anotherembodiment of the invention, a hydrocracking catalyst composition ofrelatively uniform selectivity for middle distillates is prepared asdescribed above with the additional step of incorporating at least onehydrogenation component, preferably a component containing a metalselected from Group VIA and/or Group VIII of the Periodic Table ofElements, into the steam calcined extrudates. As used herein "PeriodicTable of Elements" refers to the version officially approved by theInternational Union of Pure and Applied Chemistry (IUPAC) in its 1970rules. An example of such a table may be found in the inside back coverof the book entitled "Advanced Inorganic Chemistry," fourth edition,which is authored by F. A. Cotton and G. Wilkinson and was published in1980 by Wiley Interscience of New York.

Preferred inorganic refractory oxide components for use in the catalystof the invention are pillared clays and a dispersion of silica-aluminain an alumina matrix. A preferred crystalline aluminosilicate zeolitefor use in the catalyst is a steam stabilized modified Y zeoliteprepared by a process comprising the steps of (1) ammonium exchanging asodium Y zeolite to a sodium content between about 0.6 and 5 weightpercent, calculated as Na₂ O, (2) calcining the ammoni-um-exchangedzeolite at a temperature between about 600° F. and about 1650° F. in thepresence of steam at a water vapor partial pressure of at least about0.2 p.s.i.a. to reduce the unit cell size of said ammonium-exchangedzeolite to a value in the range between about 24.40 and about 24.64Angstroms, and (3) ammonium exchanging the steam calcined zeolite toreduce the sodium content of the zeolite below about 0.6 weight percent,calculated as Na₂ O.

The catalyst extrudates are normally calcined in the presence of asufficient amount of added steam and under conditions such that the unitcell size of the zeolite is reduced at least about 0.10 Angstroms to avalue between about 24.20 and about 24.45 Angstroms, preferably betweenabout 24.20 and about 24.39 Angstroms, most preferably between about24.20 and 24.35 Angstroms. The residence time, temperature, and watervapor partial pressure utilized during calcination of the extrudateswill typically be the same as the residence time, temperature and watervapor partial pressure required to reduce the sorptive capacity of thezeolite for water vapor to less than about 5 weight percent, preferablyless than about 4 weight percent, of the zeolite at 25° C. and a p/p°value of 0.10 if the zeolite is calcined in steam alone without firstbeing combined with other components to form extrudates. As used herein"p/p°" represents the water vapor partial pressure to which the zeoliteis exposed divided by the water vapor partial pressure at 25° C.

Catalysts of the invention have been found to have consistently highselectivities for producing middle distillates from heavy gas oils.Since variance in catalyst selectivity for middle distillates is avoidedby postponing the steaming step until after the zeolite powder has beencombined with the refractory oxide component and other constituents ofthe catalyst in the form of extrudates, the steaming step may besubstituted for the air calcination of the extrudates, a step normallyemployed in preparing hydrocracking catalysts, thereby reducing thenumber of steps necessary to manufacture the catalyst of the inventionand also decreasing the cost of manufacturing.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the invention, a hydrocarbon conversion catalyst isprepared by extruding a mixture of at least one amorphous or crystallineinorganic refractory oxide component and at least one crystallinealuminosilicate zeolite having cracking activity into extrudates whichare then broken into desired lengths and calcined in the presence ofsteam at a water vapor partial pressure greater than about 2.0 p.s.i.a.As used herein "extruding" includes all forms of pelleting includingtableting, extruding, prilling and the like. A midbarrel hydrocrackingcatalyst may be prepared by adding one or more hydrogenation componentsto the mixture of inorganic refractory oxide and zeolite that isextruded or by impregnating the steam calcined extrudates with asolution containing one or more hydrogenation components. The steamcalcination step is carried out in the presence of sufficient steam,which may be added or generated in-situ, under conditions such that theunit cell size of the zeolite is normally reduced at least about 0.10Angstroms to a value between about 24.20 and about 24.45 Angstroms. Thewater vapor partial pressure, residence time and temperature utilizedduring the steam calcination will be such that, if the zeolite particlesare calcined alone in steam under these same conditions prior to beingcomposited with the inorganic refractory oxide and formed intoextrudates, the sorptive capacity of the zeolite for water vapor will beless than 5 weight percent of said zeolite at 25° C. and a p/p° value of0.10. Thus, the zeolite in the steamed catalyst extrudates will beultrahydrophobic. Catalysts containing zeolites that are converted toultrahydrophobic zeolites by steaming after the zeolite has beencomposited with other components and formed into extrudates have beenfound to have selectivities for producing middle distillates which donot substantially vary from one catalyst batch to another.

The invention is based, at least in part, upon the discovery that, ifthe zeolite component of a catalyst is steamed prior to compositing thezeolite powder with the refractory oxide component and forming theextrudates, the selectivity of the resultant catalyst for middledistillate products is quite variable, with some batches having highselectivities and other batches having low selectivities. It is believedthat this variance in selectivity is the direct result of the smallparticles that comprise the zeolite powder. Such particles typicallyrange in size between about 0.10 and about 10 microns in diameter.During commercial production it is normal practice to calcine thesesmall zeolite particles in the presence of added steam in an inclinedrotary kiln furnace. The small particles of zeolite are introduced atthe entrance of the furnace from where they pass at an inclinedownwardly usually in countercurrent or cocurrent contact with steamwhich is typically introduced into the exit or entrance of the furnace.Alternatively, the steam may be introduced axially into the furnacethrough a perforated pipe located in the center of the furnace andrunning the length of the furnace. Because of the small size of thezeolite particles, it is very difficult to obtain an even distributionof the particles as they flow through the furnace in contact with thesteam. Some of the particles may travel faster through the furnace thanothers, while a large number of particles may travel preferentially downthe walls of the furnace or through the center of the furnace. As aresult only a portion of the zeolite particles are subjected to steamunder the proper conditions required to convert the particles to thedesired ultrahydrophobic zeolite. In the extreme, some of the particlesmay contact so much steam that substantially all of the structuralaluminum in the particles is removed, thereby converting the zeoliteparticles into inactive quartz. Other particles may contact too littlesteam thus resulting in particles containing too much structuralaluminum. The particles of zeolite that have been nonuniformly calcinedwith steam may not have the desired unit cell size, water sorptivecapacity or other properties required of the ultrahydrophobic zeolitethat, when combined with a refractory oxide component and hydrogenationmetal components, results in a hydrocracking catalyst having a highselectivity for middle distillates.

It has been found that the above-discussed problem can be avoided byeliminating the direct steaming of the zeolite powder and insteadcompositing the zeolite powder with the refractory oxide component orcomponents in the form of extrudates which can then be subjected tosteam calcination --instead of air calcination--under conditions,including the proper water vapor partial pressure, residence time, andtemperature, to convert the original zeolite in the extrudates into thedesired ultrahydrophobic zeolite. The steam calcination step may becarried in an inclined rotary kiln furnace as before but since thecatalyst particles are now in the form of extrudates, which willnormally have a diameter of at least about 1/32 of an inch and are muchlarger than the original zeolite particles, they will pass uniformlythrough the furnace in such a fashion that the individual particlescontact approximately the same amount of steam at about the sametemperature for approximately the same time. The end result is theproduction of a catalyst which will not have substantially differentselectivities from one batch to another.

Suitable zeolitic starting materials for use in preparing the catalystof the invention include crystalline aluminosilicate zeolites which havecatalytic activity for cracking hydrocarbons, a sorptive capacity forwater vapor greater than 6.0 weight percent of the zeolite at 25° C. anda p/p° value of 0.10, and a unit cell size between about 24.40 and about24.95 Angstroms. Examples of such zeolites include Y zeolites, modifiedY zeolites, X zeolites and modified X zeolites. Preferably, the startingzeolite will have a pore size above about 7.0 Angstroms, will becomprised of 12-membered rings of oxygen atoms, and will nonselectivelysorb n-hexane, 2,2-dimethylbutane and larger molecules. The mostpreferred zeolites for use in preparing the catalyst are crystallinealuminosilicate Y zeolites and modified Y zeolites. U.S. Pat. No.3,130,007, the disclosure of which is hereby incorporated by referencein its entirety, describes Y-type zeolites having an overallsilica-to-alumina mole ratio between about 3.0 and about 6.0, with atypical Y zeolite having an overall silica-to-alumina mole ratio ofabout 5.0.

The modified Y zeolites suitable for use in preparing the catalyst aregenerally derived from Y zeolites by treatment which results in asignificant modification of the Y zeolite framework structure, usuallyan increase in the framework silica-to-alumina mole ratio to a valuetypically above 6.0. It will be understood, however, that, in convertinga Y zeolite starting material to a modified Y zeolite useful in thepresent invention, the resulting modified Y zeolite may not have exactlythe same X-ray powder diffraction pattern for Y zeolites as is disclosedin U.S. Pat. No. 3,130,007. The d-spacings may be shifted somewhat dueto a shrinkage in the unit cell size caused by an increase in theframework silica-to-alumina mole ratio. The essential crystal structureof the Y zeolite will, however, be retained so that the essential X-raypowder diffraction pattern of the modified zeolite used in the crackingcatalyst will be consistent with that of either Y zeolite itself or a Yzeolite of reduced unit cell size. Examples of modified Y zeolites thatcan be used in preparing the catalyst include ultrastable Y zeolites,steam-stabilized Y zeolites and dealuminated Y zeolites.

Steam-stabilized Y zeolites are Y zeolites which have beenhydrothermally treated to increase the framework silica-to-alumina moleratio but not the overall silica-to-alumina mole ratio of the zeolite.Steam stabilization normally involves calcination of the ammonium orhydrogen form of the Y zeolite starting material at relatively hightemperatures, typically above about 900° F., in the presence of steam.This treatment results in the expulsion of tetrahedral aluminum fromframework into nonframework positions, but normally does not remove thealuminum from the zeolite and therefore does not increase the overallsilica-to-alumina mole ratio of the starting Y zeolite.

A preferred steam stabilized Y zeolite for use as the starting zeolitein preparing the catalyst of the invention is one produced by firstammonium exchanging a Y zeolite to a sodium content between about 0.6and 5 weight percent, calculated as Na₂ O, calcining theammonium-exchanged zeolite at a temperature between about 600° F. and1650° F. in the presence of steam at a water vapor partial pressure ofat least 0.2 p.s.i.a. to reduce the unit cell size of theammonium-exchanged zeolite to a value in the range between about 24.40and 24.64 Angstroms, and then ammonium exchanging the steam calcinedzeolite to replace at least 25 percent of the residual sodium ions andobtain a zeolite product of less than about 1.0 weight percent sodium,preferably less than about 0.6 weight percent sodium, calculated as Na₂O. Such a Y zeolite is highly stable and maintains a high activity. Thezeolite is described in detail in U.S. Pat. No. 3,929,672, thedisclosure of which is hereby incorporated by reference in its entirety.The same or similar zeolites are sold by the Linde Division of UnionCarbide Corporation as LZY-82 zeolite, by PQ Corporation as CP300-56 andby Conteka-BV as CBV-530 and CBV-531. The ammonium exchange stepsdescribed above may be facilitated by adding an acid to the ammoniumsolutions utilized in carrying out the exchanges.

Another preferred steam stabilized Y zeolite is prepared in the samemanner as described above except that, instead of exchanging the steamcalcined zeolite with ammonium ions, the zeolite is leached with asolution of an organic chelating agent, such as EDTA, or an inorganic ororganic acid. Preferably, the steam calcined zeolite is leached with adilute solution of hydrochloric or sulfuric acid ranging inconcentration between about 0.01N and about 10N. Zeolites prepared inthe above-described manner are disclosed in U.K. patent application2,114,594 published Aug. 24, 1983, the disclosure of which is herebyincorporated by reference in its entirety.

The dealuminated Y zeolites that can be used as the starting zeolite forpreparing the catalyst are Y zeolites which have been chemically treatedwith acids, salts, or chelating agents to increase the overallsilica-to-alumina mole ratio. A preferred group of dealuminated zeolitesis prepared by dealuminating a Y zeolite having an overallsilica-to-alumina mole ratio below about 6.0 and is described in detailin U.S. Pat. Nos. 4,503,023 and 4,711,720, the disclosures of whichpatents are hereby incorporated by reference in their entireties. Apreferred member of this group is known as LZ-210, a zeoliticaluminosilicate molecular sieve available from the Linde Division of theUnion Carbide Corporation. LZ-210 zeolites and other zeolites of thisgroup are conveniently prepared from a Y zeolite starting material inoverall silica-to-alumina mole ratios between about 6.0 and about 20,although higher ratios are possible. Preferred LZ-210 zeolites have anoverall silica-to-alumina mole ratio of about 6.1 to about 16.Typically, the unit cell size is at or below 24.65 Angstroms and willnormally range between about 24.40 and about 24.60 Angstroms. LZ-210zeolites having an overall silica-to-alumina mole ratio below 20generally have a sorptive capacity for water vapor of at least 20 weightpercent based on the anhydrous weight of the zeolite at 25° C. and 4.6millimeters mercury water vapor partial pressure. Normally, the oxygensorptive capacity at 100 millimeters mercury and -183° C. will be atleast 25 weight percent. In general, LZ-210 zeolites are prepared bytreating Y zeolites with an aqueous solution of a fluorosilicate salt,preferably a solution of ammonium hexafluorosilicate.

The stability and/or acidity of the starting zeolite may be increased byexchanging the zeolite with ammonium ions, polyvalent metal cations,such as rare earth-containing cations, magnesium cations or calciumcations, or a combination of ammonium ions and polyvalent metal cations,thereby lowering the sodium content until it is less than about 0.8weight percent, preferably less than about 0.5 weight percent and mostpreferably less than about 0.3 weight percent, calculated as Na₂ O.Methods of carrying out the ion exchange are well known in the art.

In accordance with the invention, the crystalline aluminosilicatezeolite starting material is combined with one or more inorganicrefractory oxide components, or precursors thereof, such as alumina,silica, titania, magnesia, zirconia, beryllia, a pillared or delaminatedclay, a naturally occurring clay such as kaolin, hectorite, sepiolite,attapulgite, montmorillonite or beidellite, silica-alumina,silica-magnesia, silica-titania, mixtures thereof, other suchcombinations and the like. Examples of precursors that may be usedinclude peptized alumina, alumina gel, hydrated alumina, silica-aluminahydrogels, silica sols and the flocculated reaction product between aswelling clay and a pillaring agent such as polyoxymetal cations andcolloidal particles of silica, alumina, titania and the like. Theinorganic refractory oxide components or precursors thereof, which serveas a matrix for the zeolite, may be amorphous or crystalline and areusually mixed or comulled with the aluminosilicate zeolite in amountssuch that the final dry catalyst mixture will comprise (1) between about2 and about 80 weight percent zeolite, preferably between about 5 andabout 50 weight percent, and (2) between about 20 and about 98 weightpercent of one or more inorganic refractory oxides, preferably betweenabout 30 and about 80 weight percent. In some cases where the matrix isnot capable of sufficiently binding with the zeolite, an inorganicrefractory oxide such as peptized alumina may be used as a portion ofthe matrix where it serves as a binder.

A preferred inorganic refractory oxide component for use in preparingthe catalyst is a heterogeneous dispersion of finely dividedsilica-alumina in an alumina matrix. Such a material is described indetail in U.S. Pat. Nos. 4,097,365 and 4,419,271, the disclosures ofwhich are hereby incorporated by reference in their entireties. Oneconvenient method of preparing the dispersion is to comull an aluminahydrogel with a silica-alumina cogel in hydrous or dry form.Alternately, the alumina hydrogel may be comulled with a "graftcopolymer" of silica and alumina that has been prepared, for example, byfirst impregnating a silica hydrogel with an alumina salt and thenprecipitating alumina gel in the pores of the silica hydrogel by contactwith ammonium hydroxide. In the usual case, the cogel or copolymer ismulled with the alumina hydrogel such that the cogel or copolymercomprises between about 5 and 75 weight percent, preferably 20 to 65weight percent of the mixture. The overall silica content of theresulting dispersion on a dry basis is normally between about 1 andabout 75 weight percent, preferably between about 5 and about 45 weightpercent. Typically, the silica-alumina is dispersed in a gamma aluminamatrix.

Other preferred inorganic refractory oxide components that can be usedin preparing the catalyst include pillared and delaminated clays.Pillared clays are typically formed by intercalating thermally stable,robust, three dimensional cations, colloidal particles and othermaterials between the silicate layers or platelets of smectite clays.The shape and size of the intercalated materials allows them to serve asmolecular pillars to prop apart the layers of the clay and therebyprevent them from collapsing. The fairly homogeneous distribution ofpillars in the interlayered spaces of the clay form an array ofrectangular openings, typically about 8 by 15 Angstroms in size, whichenable the pillared clay to behave like a 2 dimensional sieve. Byadjusting the size of the pillars or the spacing between such pillars,or both, the pore size of the pillared clay may be adjusted to suit aparticular application. Pillared clays are typically prepared byintercalating montmorillonite, hectorite, and beidellite, the mostcommon of the smectite clays, with polyoxycations, preferablypolyoxycations of aluminum, zirconium, and mixtures of aluminum andzirconium. Pillared clays and their preparation are described more fullyin the article entitled "Intercalated Clay Catalysts," Science, Volume220, No. 4595, pp. 365-371 (Apr. 22, 1983) and in U.S. Pat. Nos.4,176,090, 4,248,739 and 4,216,188. The disclosures of theaforementioned article and patents are hereby incorporated by referencein their entireties. Pillared clays may be optionally treated with steamprior to being combined with the zeolite component of the catalyst andformed into the extrudate particles which are subjected to steamcalcination.

A suitable pillared smectite clay for use as a component of the catalystcomprises pillars interposed between the platelets of the clay such thatthe spacing between the platelets ranges from about 6.0 to about 10Angstroms and is maintained at such values when the clay is heated tohigh temperatures. Examples of pillared clays possessing such stabilityat high temperatures are ones in which the pillars contain one or morerare earth elements such as cerium and/or lanthanum. Such clays aredisclosed in U.S. Pat. No. 4,753,909 and in PCT Applications WO 88/06614and WO 88/06488, the disclosures of which are hereby incorporated byreference in their entireties, and are taught in PCT Application WO88/06614 to possess outstanding catalytic activity and selectivity inhydrocracking to produce middle distillate products.

The polyoxycations and other agents typically used to pillar smectiteclays can also be used to delaminate certain types of clays. Unlikepillared clays in which the propped-apart platelets are oriented face toface, the platelets in a delaminated clay, some of which platelets arepropped apart by metal pillars, contain edge-to-edge and edge-to-facelinkages or connections which form a macrospace of the type found inamorphous aluminosilicate supports. Delaminated clays can be prepared byreacting Laponite, a synthetic hectorite manufactured by LaporteIndustries, Ltd. and other trioctahedral smectite clays having alath-shape morphology with polyoxymetal cations, colloidal metal andmetal oxide particles, and cationic metal clusters as described in U.S.Pat. Nos. 4,629,712 and 4,761,391, the disclosures of which are herebyincorporated by reference in their entireties.

The desired inorganic refractory oxide component(s) or precursor(s)thereof is typically mulled, normally in the form of a powder, with thestarting zeolite particles, which particles are preferably not subjectedto a steam treatment just prior to being combined with the refractoryoxide component. If desired, a binder such as peptized alumina may alsobe incorporated into the mulling mixture, as also may one or more activemetal hydrogenation components such as ammonium heptamolybdate, nickelnitrate, ammonium metatungstate, cobalt nitrate, molybdenum oxide,cobalt oxide, nickel oxide, tungsten oxide and the like. After mulling,the mixture is extruded through a die having openings of a crosssectional size and shape desired in the final catalyst particles. Forexample, the die may have circular openings to produce cylindricalextrudates or openings in the shape of 3-leaf clovers so as to producean extrudate material similar to that shown in FIGS. 8 and 8A of U.S.Pat. No. 4,028,227, the disclosure of which is hereby incorporated byreference in its entirety. Among preferred shapes for the die openingsare those that result in particles having surface-to-volume ratiosgreater than about 100 reciprocal inches. If the die opening is notcircular in shape, it is normally desirable that the opening be in ashape such that the surface-to-volume ratio of the extruded particles isgreater than that of a cylinder. After extrusion, the extruded catalystparticles are broken into lengths of from 1/16 to 1/2 inch. Theeffective diameter of the extruded particles will normally range betweenabout 1/40 and 1/8 of an inch. The extruded particles will be quitelarge when compared to the size of the zeolite particles that are mulledto form the material that is extruded. Normally, the effective diameterof the extruded particles will range between about 50 and about 200times greater than the diameter of the zeolite particles.

After the extruded catalyst particles are broken into the desiredlengths and before they are subjected to any potential air calcination,they are subjected to steam calcination by heating the extrudateparticles in the presence of water vapor to at least about 500° C.,usually between about 600° C. and about 870° C., and preferably in therange between about 700° C. and about 850° C. The steam calcination isnormally carried out at a total pressure ranging between about 7.5p.s.i.a. and about 3000 p.s.i.a., preferably between about 15 p.s.i.a.and above 1500 p.s.i.a. The water vapor partial pressure during thesteam calcination will usually range from above about 2.0 p.s.i.a. toabout 150 p.s.i.a., preferably from about 5.0 p.s.i.a. to about 35p.s.i.a. In a preferred embodiment, the steam calcination step isperformed in the presence of a gaseous atmosphere consisting essentiallyof water vapor and most preferably at about atmospheric pressure.

The steam calcination is generally carried out for a period of timecorrelated with the severity of the calcination conditions, especiallythe water vapor partial pressure and the calcination temperature, so asto convert the zeolite in the extrudates to an ultrahydrophobic zeolite.The desired ultrahydrophobic zeolites have a unit cell size betweenabout 24.20 and about 24.45 Angstroms, preferably between about 24.20and 24.39 Angstroms, most preferably between about 24.20 and 24.35Angstroms, and a sorptive capacity for water vapor less than about 5weight percent, preferably less than about 4 weight percent, of thezeolite at 25° C. and a p/p° value of 0.10. The zeolites are the same orsimilar to the UHP-Y zeolites disclosed in U.S. Pat. No. 4,401,556 andU.K. Pat. No. 2,014,970 published on Jun. 29, 1982, the disclosure ofthe latter patent being hereby incorporated by reference in itsentirety. According to these references, a UHP-Y zeolite is defined as azeolite having a silica-to-alumina mole ratio of from 4.5 to 35, theessential X-ray powder diffraction pattern of zeolite Y, an ion exchangecapacity of not greater than 0.070, a unit cell size from 24.20 to 24.45Angstroms, a surface area of at least 350 meters² /gram (B-E-T), asorptive capacity for water vapor less than 5 weight percent at 25° C.and a p/p° value of 0.10, and a Residual Butanol Test Value of not morethan 0.4 weight percent. The Residual Butanol Test is a measure of theadsorptive selectivity of zeolite adsorbents for relatively nonpolarorganic molecules under conditions in which there is active competitionbetween water and less polar molecules for adsorption on the zeolite.The test procedure is described in detail in the above-identifiedpatents.

Preferably, the steam calcination is carried out under conditions suchthat the ultrahydrophobic zeolite formed during the calcination has asilica-to-alumina mole ratio between about 4.5 and about 9, theessential X-ray powder diffraction pattern of zeolite Y, an ion-exchangecapacity of not greater than 0.070, and a Residual Butanol Test Value ofnot more than 0.4 weight percent. More preferably, the steam calcinationis carried out under conditions such that LZ-10 zeolite is formed. LZ-10zeolite is a modified Y zeolite having a silica-to-alumina mole ratiobetween about 4.5 and about 6.0, a surface area between about 500 and700 meters2/gram, a unit cell size between about 24.20 and about 24.35Angstroms, and a sorptive capacity for water vapor less than about 5percent by weight of the zeolite at 25° C. and a p/p° value of 0.10.

The steam calcination treatment may be carried out by any number ofprocedures. In one method, the wet extrudates are merely heated in anenclosed vessel which prevents the escape of water vapor generated insitu. Alternatively, the extrudates may be heated in an autoclaveequipped with a pressure relief valve such that superatmosphericpressures of steam may be obtained therein. In yet another procedure,the extrudates may be introduced into a batch or continuous static bedcalcination zone into which preheated steam or humidified air is alsointroduced. Most preferably, however, the extrudates are calcined in aninclined rotary kiln furnace by introducing the extrudates into the kilnat the entrance so that they pass downwardly at an incline in contactwith steam that is introduced into the exit of the furnace, into theentrance of the furnace, or through a perforated pipe located in thecenter of the furnace and running the length of the furnace. Because therelatively small zeolite particles are incorporated into the relativelylarge extrudate particles, which because of their size are uniformlycontacted with steam during the calcination step, the zeolite particlesare easily and consistently converted to the desired ultrahydrophobiczeolite.

As mentioned previously, hydrogenation components may be mulled with thezeolite and the inorganic refractory oxide component to form theextrudates which are subsequently subjected to steam calcination.Alternatively, the hydrogenation components may be added by impregnationafter the steam calcination step. The hydrogenation component orcomponents may be impregnated into the steam calcined extrudates from aliquid solution containing the desired hydrogenation component orcomponents in dissolved form. In some cases it may be desirable to ionexchange the steam calcined extrudates with ammonium ions prior toadding the hydrogenation metal component or components. This may be doneby slurrying the extrudates in a solution of an ammonium salt until thesodium content of the extrudates is decreased below about 0.2 weightpercent, calculated as Na₂ O. Hydrogenation components suitable forincorporation into the catalyst extrudates comprise metals selected fromGroup VIII or Group VIA of the Periodic Table of Elements. Preferredhydrogenation components comprise metals selected from the groupconsisting of platinum, palladium, cobalt, nickel, tungsten, chromiumand molybdenum. In some cases, it may be desirable that the catalystcontain at least one Group VIII metal component and at least one GroupVIA metal component. When this is the case, the preferred combinationwill normally be a nickel and/or cobalt component with a molybdenumand/or tungsten component.

If the hydrogenation component comprises a noble metal, it is generallydesired that the dissolved hydrogenation component be present in theimpregnation liquid in a proportion sufficient to ensure that thecatalyst contains between about 0.05 and about 10 weight percent of thehydrogenation component, preferably between about 0.10 weight percentand about 3.0 weight percent, calculated as the metal. If thehydrogenation component comprises a non-noble metal, however, it isnormally desired that the dissolved hydrogenation component be presentin the impregnation liquid in a proportion sufficient to ensure that thecatalyst contains between about 1.0 and about 40 weight percent of thehydrogenation component, preferably between about 10 weight percent andabout 30 weight percent, calculated as the metal oxide. After thesteamed extrudates have been impregnated with the solution containingthe hydrogenation component or components, the particles are dried andcalcined in air to produce the finished catalyst particles.

Hydrocarbon conversion catalysts prepared as described above are usefulin the conversion of a wide variety of hydrocarbon feedstocks tomidbarrel products boiling in the range between about 300° F. and about700° F. If the catalyst does not contain a hydrogenation component, itmay be utilized in the absence of added hydrogen as a catalyst forconverting hydrocarbons to more valuable products by acid catalyzedreactions, such as catalytic cracking, isomerization of n-paraffins toisoparaffins, isomerization of alkyl aromatics, alkylation, andtransalkylation of alkyl aromatics. As used herein "hydrocarbon" refersto any compound which comprises hydrogen and carbon, and "hydrocarbonfeedstock" refers to any charge stock which contains greater than about80 weight percent carbon and hydrogen, calculated as the elements. Ifthe catalyst contains one or more hydrogenation components, it may beused to convert feedstocks in the presence of added hydrogen to amidbarrel hydroconversion product boiling between about 300° F. andabout 700° F. The feedstocks that may be subjected to hydrocarbonconversion by the method of the invention include mineral oils, andsynthetic oils such as shale oil, oil derived from tar sands, coalliquids and the like. Examples of appropriate feedstocks forhydroconversion include straight run gas oils, vacuum gas oils, andcatalytic cracker distillates. Preferred hydroconversion feedstocksinclude gas oils and other hydrocarbon fractions having at least 50weight percent of their components boiling above 700° F.

The catalyst of the invention will usually be employed as a fixed bed ofcatalytic extrudates in a hydroconversion reactor into which hydrogenand the feedstock are introduced and passed in a downwardly direction.The reactor vessel is maintained at conditions so as to convert thefeedstock into the desired product, which is normally a hydrocarbonproduct containing a substantial proportion of turbine fuel and dieselfuel components boiling in the range between 300° F. and 700° F. Ingeneral, the temperature of the reaction vessel is maintained betweenabout 450° F. and about 850° F., preferably between about 600° F. and800° F. The pressure will normally range between about 750 p.s.i.g. andabout 3500 p.s.i.g., preferably between about 1000 p.s.i.g. and about3000 p.s.i.g. The liquid hourly space velocity (LHSV) is typicallybetween about 0.3 and about 5.0, preferably between about 0.5 and 3.0.The ratio of hydrogen gas to feedstock utilized will usually rangebetween about 1000 and about 10,000 standard cubic feet per barrel,preferably between about 2000 and about 8000 standard cubic feet perbarrel as measured at 60° F. and one atmosphere.

It will be apparent from the foregoing that the invention is primarilydirected to a hydrocracking catalyst prepared in such a fashion that theselectivity of the catalyst for producing midbarrel products boilingbetween 300° F. and 700° F. from feedstocks containing a substantialproportion of material boiling above 700° F. remains constant from batchto batch. Moreover, the procedure for preparing the catalyst results ina less complicated and cheaper method of catalyst manufacturing.

Although this invention has been primarily described in conjunction withpreferred embodiments thereof, it is evident that many alternatives,modifications and variations will be apparent to those skilled in theart in light of the foregoing description. Accordingly, it is intendedto embrace within the invention all such alternatives, modifications andvariations that fall within the spirit and scope of the appended claims.

I claim:
 1. A process for making a hydrocarbon conversion catalyst whichcomprises:(a) extruding a mixture of a first inorganic refractory oxidecomponent, a second inorganic refractory oxide component and a modifiedY zeolite, and (b) calcining said extrudates in the presence of steam ata water vapor partial pressure greater than about 5.0 p.s.i.a. underconditions such that the unit cell size of said modified Y zeolite isreduced to a value between about 24.20 and about 24.45 angstroms.
 2. Aprocess as defined by claim 1 which further comprises impregnating saidcalcined extrudates with at least one metal hydrogenation component. 3.A process as defined by claim 2 wherein said mixture in step (a) isdevoid of a metal hydrogenation component.
 4. A process as defined byclaim 3 wherein after said calcination said second inorganic refractoryoxide serves as a binder for said first inorganic refractory oxidecomponent and said zeolite.
 5. A process as defined by claim 4 whereinsaid second inorganic refractory oxide component comprises peptizedalumina.
 6. A process as defined by claim 5 wherein said first inorganicrefractory oxide component comprises a dispersion of silica-alumina inalumina.
 7. A process as defined by claim 5 wherein said first inorganicrefractory oxide component comprises silica-alumina.
 8. A process asdefined by claim 1 wherein said calcination takes place in a gaseousatmosphere consisting essentially of steam.
 9. A process as defined byclaim 3 wherein said extrudates are calcined under conditions such thatthe unit cell size of said zeolite is reduced at least about 0.10angstroms.
 10. A process as defined by claim 3 wherein said extrudatesare calcined under conditions such that the unit cell size of saidzeolite is reduced to a value between 24.20 and 24.39 angstroms.
 11. Acatalyst composition prepared by the process of claim
 1. 12. A catalystcomposition as defined by claim 11 devoid of a metal hydrogenationcomponent.
 13. A catalyst composition comprising a zeolite, at least oneinorganic refractory oxide, and at least one metal hydrogenationcomponent, said catalyst composition prepared by a processcomprising:(a) extruding a mixture of at least one inorganic refractoryoxide component and a crystalline aluminosilicate zeolite havingcracking activity and an overall silica-to-alumina mole ratio betweenabout 3.0 and about 60 to form extrudates, wherein said mixture isdevoid of a metal hydrogenation component; (b) calcining said extrudatesin the presence of steam at a water vapor partial pressure greater thanabout 5.0 p.s.i.a. under conditions such that the unit cell size of saidcrystalline aluminosilicate zeolite is reduced to a value between about24.20 and about 24.45 angstroms; and (c) impregnating said calcinedextrudates with at least one metal hydrogenation component.
 14. Acatalyst composition as defined by claim 13 wherein said crystallinealuminosilicate zeolite used in step (a) is prepared by a processcomprising the steps of (1) ammonium exchanging a sodium Y zeolite to asodium content between about 0.6 and about 5 weight percent, calculatedas Na₂ O, (2) calcining the ammonium-exchanged zeolite at a temperaturebetween about 600° F. and about 1650° F. in the presence of steam at awater vapor partial pressure of at least about 0.2 p.s.i.a. to reducethe unit cell size of said ammonium-exchanged zeolite to a value in therange between about 24.40 and about 24.64 angstroms, and (3) ammoniumexchanging the steam calcined zeolite to reduce the sodium content ofthe zeolite below about 0.6 weight percent, calculated as Na₂ O.
 15. Acatalyst composition as defined by claim 13 wherein said crystallinealuminosilicate Y zeolite used in step (a) is prepared by a processcomprising (1) ammonium exchanging a sodium Y zeolite to a sodiumcontent between about 0.6 and about 5 weight percent, calculated as Na₂O, (2) calcining the ammonium-exchanged zeolite at a temperature betweenabout 600° F. and about 1650° F. in the presence of steam at a watervapor partial pressure of at least about 0.2 p.s.i.a. to reduce the unitcell size of said ammonium-exchanged zeolite to a value in the rangebetween about 24.40 and 24.64 angstroms, and (3) leaching the steamcalcined zeolite with a solution comprising an inorganic or organicacid.
 16. A catalyst composition as defined by claim 13 wherein saidextrudates have a surface-to-volume ratio greater than that of acylinder.
 17. A catalyst composition as defined by claim 13 wherein saidextrudates have the cross sectional shape of a three-leaf clover.
 18. Acatalyst composition as defined by claim 13 wherein said extrudates havethe cross sectional shape of a cylinder.
 19. A catalyst composition asdefined by claim 13 wherein said crystalline aluminosilicate zeoliteused in step (a) comprises a modified Y zeolite selected from the groupconsisting of ultrastable Y zeolites, steam-stabilized Y zeolites, anddealuminated Y zeolites.
 20. A catalyst composition as defined by claim13 which comprises said zeolite, a dispersion of silica-alumina inalumina, and an alumina binder.
 21. A catalyst composition as defined byclaim 13 which comprises said zeolite, a silica-alumina component, andan alumina binder.
 22. A catalyst composition as defined by claim 13wherein said crystalline aluminosilicate used in step (a) comprises lessthan about 0.6 weight percent sodium, calculated as Na₂ O.
 23. Acatalyst composition as defined by claim 13 wherein the overallsilica-to-alumina mole ratio of said crystalline aluminosilicate zeoliteis between about 3.0 and about
 20. 24. A process for making ahydrocarbon conversion catalyst which consists essentially of:(a)extruding a mixture of at least one inorganic refractory oxide componentand a crystalline aluminosilicate zeolite having cracking activity andan overall silica-to-alumina mole ratio between about 3.0 and about 60to form extrudates; (b) calcining said extrudates in the presence ofsteam at a water vapor partial pressure greater than about 5.0 p.s.i.a.under conditions such that the unit cell size of said crystallinealuminosilicate zeolite is reduced to a value between about 24.20 andabout 24.45 angstroms; and (c) impregnating said calcined extrudateswith at least one metal hydrogenation component.
 25. A catalystcomposition prepared by the process of claim 24.